Numbers: Conditional Formatting

I am familiar with Excel, less so with Numbers. I am trying to use conditional formatting in Numbers and, it seems less well implemented? Perhaps someone can explain how this could work? To the point, I cannot get a cell that shows the result of a formula to work in conditional formatting. Neither can I select an areas of cells and combine the formatting as this is about a single cell value being compared and not a cell to cell relative comparison in the same way if I dragged out a cell to cell formula (it would populate the formula relative to all the cells in the new dragged out area).

I am trying to compare two columns. If the results in cell A2 are the same as in cell B2 then, there would be no added formatting. If on the other hand, cell A2 and cell B2 are not equal, then the formatting should make the text in cell B2 red. Once I get this done correctly then I also want to apply it to the rest of the cells in the two columns.

This is not working. The problem seems to be that column B is holding the result of a calculation and therefore is not able to be read in the conditional highlight formula? This makes no sense at all that it has been engineered this way. As I have searched at length before posting this, some speak of adding a third cell, but as the value I need must be calculated, I cannot see how this is supposed to work - even in a work-around?

This is a project where I am getting a handle on an overdraft account that got away from me. I am comparing the banks monthly interest charges in column A with the result of my formula in column B, which calculates what the interest should be, based on the banks own supplied formula. These two cells should match exactly and where it is off, I want to notice it. That is why once I get it working in two cells, I want to apply it to results in both columns. But again, there seems no way to do this?